Objectives: This study investigated the surface hardness of thin layer in two dual-cured resin luting cements (Clapearl DC and Nexus 2) irradiated through or not through 2.0 mm thick machinable ceramics. Methods: A piece of adhesive polyethylene tape with a circular hole 5 mm in diameter was positioned on the ceramic surface to control the cement layer (approximately 50 µm). The cement paste was placed on the ceramic surface within the circle. The ceramic plate with cement was placed on a clear micro cover glass over a zirconia ceramic block to obtain a flat surface. The material was polymerized through ceramic using a visible-light-curing unit for 40 s. Other specimens were irradiated directly on the glass (not through ceramic). Five measurements of surface hardness were recorded immediately after irradiation and at post-irradiation times of 0.5, 1, 2, 4, 8, and 24 h. Data were analyzed by three-way ANOVA and Fisher's Protected LSD test (p<0.05). Results: The increase in hardness was relatively rapid over the first 30 min and continued at a lower rate thereafter. The resin cements cured through ceramic were significantly less hard compared with those cured not through ceramic at all post-irradiation times. Conclusion: These results suggest that machinable ceramic thickness of 2 mm hindered maximum hardening of dual-cured resin luting cements.
|
Resin cement |
Clapearl DC |
Nexus 2 |
||
|
Ceramic spacer |
not through |
through |
not through |
through |
|
Post-irradiation time (h) |
Mean Knoop hardness number (SD) |
|||
|
0 |
27.9 (2.0) |
24.1 (0.7) |
21.5 (0.7) |
18.4 (0.8) |
|
0.5 |
31.3 (1.9) |
28.1 (0.8) |
27.4 (0.4) |
23.9 (1.4) |
|
1 |
32.1 (1.9) |
29.1 (0.7) |
29.0 (0.6) |
25.3 (1.1) |
|
2 |
33.9 (1.7) |
31.9 (1.1) |
30.0 (0.3) |
27.4 (0.5) |
|
4 |
35.7 (1.0) |
33.8 (0.7) |
31.0 (0.3) |
28.3 (0.5) |
|
8 |
37.2 (0.3) |
35.5 (1.0) |
32.0 (0.2) |
29.1 (0.8) |
|
24 |
40.1 (1.0) |
37.9 (0.8) |
35.0 (0.4) |
31.1 (0.2) |